Apparatus for digging trenches or general excavation on large construction projects is usually accomplished with a backhoe or a bulldozer. However, there is a need for a digging apparatus which may be used on small scale projects by farmers or others who have access to tractors such as may be used in a farming, sod growing or horticulture type environment.
Tractors have had three-point hitches on their rear-ends for many years and the operating features are well known and need not be described in detail. However, there are different attachment mechanisms of a minor nature as between different brands of tractors and even the same brand of tractor may have a different hook-up mechanism from one year to the next.
An example of a structure attachable to a three-point hitch on the back of a tractor is illustrated in the patent to Livesey et al., U.S. Pat. No. 2,273,875. It includes a mounting apparatus for supporting a "drag pan" which is designed to scoop loose material from some surface and then the full pan is lifted vertically and transported to a dump site where the bottom of the pan is released. Thereby, the grain, sand or the like, is dumped at the desired location by the bottom of the pan pivoting from a forward pivot axis such that the contents of the pan drain out the back.
A patent to King, U.S. Pat. No. 2,295,850, is another example of a three-point hitch connection to a rear mounted excavator for mounting on a tractor. A framework mounts a bucket with a forward cutting edge. The apparatus is structured to excavate a broad path of limited depth. The bucket is designed to dig into the soil in a trench having a width which is approximately equal to the width of the axle mounting the wide based rear wheels of the tractor. Tilting and dumping of the bucket is achieved by a manual operation controlled by the operator of the tractor using levers and cables.
A patent to Holopainen, U.S. Pat. No. 2,496,874, is another example of mounting a digging apparatus on the rear of a tractor using a three-point hitch. The mounting apparatus includes a parallelogram structure of beams separated by struts. On their lower end is a bucket designed for ditch digging. Indeed, the structure disclosed is obviously quite effective in digging shallow ditches but it is limited in its ability to penetrate to any great depth because the mounting structure of the bucket is secured to the bucket transversely of the digging edge. Therefore, the side mounting limits the depth of penetration into the soil by the bucket. More specifically, the side mountings of the bucket will not allow the bucket to extend into a trench of the same width as the bucket to any greater depth than the space between the bottom of the bucket and the bottom edge of the bucket mounting hardware. The bucket is structured to dump its contents in response to a hand operated cord connected to a spring-locked latch at one rear edge of the bucket.
A patent to Brundage et al., U.S. Pat. No. 2,930,151, discloses another apparatus for mounting a scoop on the rear of a tractor and it includes a hand manipulated cord for dumping the contents. Another feature of the Brundage et al. patent is the reversible mounting of the bucket which allows the bucket to scoop earth, grain or the like by the bucket, but the scooping operation takes place in either the forward or rear direction, depending upon the desired mounting of the bucket.
A patent to Poche, U.S. Pat. No. 3,916,543, discloses a highly mechanized trenching apparatus which includes a bucket for digging soil in a trench and an associated shredder for chopping the excavated soil and discharging it transversely of the bucket. The appearance is somewhat similar to snow being discharged by a snow blower. The depth of digging by the trenching apparatus is limited only by the height of the discharge duct located transversely of the excavation bucket and the length of the mounting arm on the rear of the tractor.
All these patents disclose a basic concept of mounting a digging or scooping apparatus on the rear of a tractor by connecting support apparatus to the three-point hitch. What they do not disclose is the concept of digging a trench of relatively narrow width such that the wheels of the tractor span the width of the trench while allowing the digging bucket to extend downwardly into the trench to a depth several times the height of the bucket itself. The structure disclosed in the above patents is relatively flimsy in its mounting and excavation components and is obviously not suited for long-term use in digging a series of deep trenches.